The ScaRaB Earth Radiation Budget Scanning Radiometer

Abstract

In order to ensure that Earth Radiation Budget measurement from space continues through the 1990s, France, Germany and the USSR are developing a Scanning Radiometer for Radiation Balance (ScaRaB) to be flown on a series of METEOR-3 Soviet polar orbiting weather satellites. The instrument described in this paper comprises two broad channels (0,2 μm to 50 μm, 0,2 μm to 4 μm) for radiation budget, and two narrower bands (0,5 μm to 0,7 μm, 10,5 μm to 12,5 μm) for scene identification, with spatial resolution at nadir of order 50 km. The set of on-board sources includes black-body simulators for the calibration of long-wave channels, and both tungsten filament lamps and mosaic array diffusers for short-wave calibration. A specific filtering scheme cancels the influence of thermal environment during calibration of the 0,2 μm to 50 μm channel on solar diffusers and lamps. Hemispherical choppers associated with pyroelectric detectors ensure a high immunity to low frequency noise and thermal transients.